bad fit with ca glue

[Crabby]

Good am comrades mates and dear friends
I was recently successfully tempted to go dark side and use ca glue on a dihedral joint. It went sideways and somehow even though I had it jigged, I lost the angles. I have tried to break such joints apart in the past with sketchy results, so I ask has anyone ever successfully reglued a bad CA joint? please tell on...

[TheLurker]

Try some cellulose thinners on the joint to separate it.  You may struggle to rejoin the wood though if the CA has soaked into the wood fibres, I've found it leaves a non-porous surface which won't "take" further adhesive.  A bit of gentle sanding sometimes gets you back to clean wood.  It is my least favourite adhesive and I try to restrict its use to field repairs only.

[Nigel M]

I've successfully re-glued a thin ply patch onto a carbon wing surface. The patch was a servo hatch and the cheap servo was a bad idea. I used CA debonder to soften the CA. It still needed a good amount of working the debonder into the overlapping joint faces. The ply was wrecked afterwards. Also, the resulting goop had to be scraped off the carbon surface with a finger nail to get it back to being useable.
Not quite the same situation, sorry.
Nigel

[Crabby]

OK I guess I'm gonna set up some lab work. The patient I am currently working with is the weird Noctule designed by Peter Fischer and loved by Al Backstrom. I needed something to sharpen up on. I have taken the wing apart at the dihedral joints and will attempt re-gluing. More later

[Rekitus]

ya ever wonder if the exception is the rule?
with a balsa model...
is more like if you use CA, stay with CA.
and I have used epoxy to repair old CA...

CA is dissolved by acetone. and if you
soak away hardened glue the goo does
not 'stick' to much...so the thinner CA options wick
into the old stuff and stick better.
use thin CA in this case.

and in a bit of why?
I thinned with acetone some CA while gluing a test joint.
the CA hardened and glued/stuck...after the acetone evaporated.
that needs tidy joints.


victor

[dorme]

The biggest problem with CA is that it won't stand up to vibration.  I glue dihedral joints and other important joints with Duco cement, or yellow glue or epoxy.  When I have a break at a joint with CA (in the past), I'll use a file instead of sandpaper.  It cuts cleaner, where sandpaper will damage a lot of the surrounding area and not cut the CA very well. I have gotten away from CA as I don't need to hurry and CA tends to go bad fairly quickly.  Some of my friends who use CA only buy the smallest amount bottles for that reason.

PS I had a tube of Ambroid up until recently but gave it to a friend because I was afraid if it got out that I had it, I might gotten hit by the "over the hill" gang when I lest expected it!

[JohnOSullivan]

CA is a good glue for tightly fitted parts but is useless for poorly fitted components. The glue, itself has very poor strength and filling a poorly joint just fills the gap with an inferior material of low strength.
 As an example, take a piece of polyethelene and make a thick puddle of med of thick CA about 3/4" diam. Allow to cure and peel off. Test it by bending it and it will snap with little force. It, as glue itself has little or no shear strength. Don't rely on CA for poorly fitted Joints.

[Starduster]

Thanks to YouTube, I fairly recently discovered a technique for gap filling with Ca. A lot of you may already know this, but keep a small container of Baking Soda on the workbench. Spread a bead of Ca, then use your fingers to sprinkle the Baking Soda along the Ca. You can (but I've found it not necessary) to use my little fingertip to smooth the Ca/Baking Soda. Works a charm. Very strong joint, and works as a Ca accelerant.

[Arnold S]

Thanks to YouTube, I fairly recently discovered a technique for gap filling with Ca. A lot of you may already know this, but keep a small container of Baking Soda on the workbench. Spread a bead of Ca, then use your fingers to sprinkle the Baking Soda along the Ca. You can (but I've found it not necessary) to use my little fingertip to smooth the Ca/Baking Soda. Works a charm. Very strong joint, and works as a Ca accelerant.

I did not know that, so will give that a go!  Good tip….Thanks! 

Andrew

[billdennis747]

Thanks to YouTube, I fairly recently discovered a technique for gap filling with Ca. A lot of you may already know this, but keep a small container of Baking Soda on the workbench. Spread a bead of Ca, then use your fingers to sprinkle the Baking Soda along the Ca. You can (but I've found it not necessary) to use my little fingertip to smooth the Ca/Baking Soda. Works a charm. Very strong joint, and works as a Ca accelerant.

I did not know that, so will give that a go!  Good tip….Thanks! 

Andrew

That reminds me that decades ago, when CA was just starting to be used by modellers but I was resistant, Eric Coates told me it was 'the new thing' and had enabled him to stick his new model together in minutes. At the same time he told me the baking soda wheeze. I still don't like it and have had more glue-related disasters than with any other type, including having entire models glued to my finger. They used to say that Colmans made their fortune by the amount of surplus mustard thrown away; similarly with gone-off cyano.

[Mike Thomas]

The biggest problem with CA is that it won't stand up to vibration. 

There are rubber toughened CAs readily available that address this issue of flexibility. One example of where it is commonly used is attaching carbon caps to wing ribs.

This is a link to one brand chosen at random.  https://www.loctiteproducts.com/en/products/fix/super-glue/loctite_super_glueultragelcontrol.html 

[billdennis747]

The biggest problem with CA is that it won't stand up to vibration. 

There are rubber toughened CAs readily available that address this issue of flexibility. One example of where it is commonly used is attaching carbon caps to wing ribs.

This is a link to one brand chosen at random.  https://www.loctiteproducts.com/en/products/fix/super-glue/loctite_super_glueultragelcontrol.html 

I didn't know that and will give it a try. I always have trouble with capstrips popping off ribs and spars.

[che]

Bill said :-  I always have trouble with capstrips popping off ribs and spars.

I assume you mean off balsa ribs and balsa spars ? The problem here is that :-

a) The carbon preparation isn't good enough. You need to remove any release agent, roughen with W&D and then clean with acetone or similar. If you don't do this then the bond will fail at the interface with the carbon.
b) CA is brittle and even rubber 'toughened' products don't produce a good bond with carbon. Use a good epoxy instead (not 5 minute).
c) A good joint will often result in failure of the balsa just below the glue line as the balsa will 'tear' off. Either reduce the impact force (!) or use harder balsa.

You are basically trying to glue a hard, stiff material with good inter-laminar strength to a soft, flaccid material that fails easily along the fibres. It does however produce and excellent stiff beam structure (spars or ribs) when it's intact.

CHE

[billdennis747]

Thanks Che; I confess to most of a)

[Arnold S]

Loctite produce some "hybrid" Adhesives, which have the best characteristics of both CA and and epoxy.  I Used them a few years back and they were very good (but being made by Loctite I guess they are expensive!)

That reminds me...The Loctite rep that used to call on me was called Simon Groom (not the one from Blue Peter!)  He was a keen aero modeller himself.  Does anyone know of him?

Andrew

[che]

That reminds me...The Loctite rep that used to call on me was called Simon Groom (not the one from Blue Peter!)  He was a keen aero modeller himself.  Does anyone know of him?

Andrew

There was a Loctite Rep called **** who was a very good FF glider flier, mostly A2, based around the Grantham area I think. He was often their top sales guy and on more than one occasion got a jolly to see the Loctite sponsored Thrust 1 runs in the US. Great guy, he eventually got fed up with Loctite and last I heard (decades ago) was selling/renting surfboards 'darn sarth'.

**** best I can come up with is Mike Croome. He was good mates with Brian Baines in anyone has contact with his.

CHE

[che]

Update. I've asked around and the name that comes up is Mike Coomes. Not sure about the spelling, it may be Coombes or similar.

Anyone else remember him ?

CHE

[cvasecuk]

My source says, "Mike Coombes" and he was the Midland Area Comp Sec. Unfortunately no information as to what he did once he dropped out of aeromodelling.
Ron